Ultra high frequency oscillator



Aug. 22, 1939. R. SEILER ULTRA HIGH FREQUENCY OSCILLATOR Filed Oct. 28, 19:57

INV EN TOR.

. 'lc RD SE/LER ATTORNEY.

Patented Aug. 22, 1939 PATENT OFFICE ULTRA HIGH FREQUENCY OSCILLATOR Richard Seller, Berlin, Germany, assignor to Telefunlrenv Gesellschaft fiir Drahtlose Telegraphie m. b. 11., Berlin, Germany, a corporation of Germany Application October 28, 1931, Serial No. 171,485

In Germany October 16, 1936 9 Claims. (Cl. 250- 275) The present invention relates to electron discharge tubes and circuits therefor. In carrying out the invention it is contemplated that by the aid of a tube of the retarding-field type it is fea- 6 sible to generate transit-time oscillations andmore particularly retarding-field or electron-oscillation waves with better efifilciency and above all without the necessity of providing additional circuit elements.

If in a retarding-field or electron-oscillation circuit arrangement the oscillatory circuit is interposed between the accelerator grid and the transit time of the electrons from the grid to the anode.

It can be shown in this connection that the transit time in the grid-cathode space has no effect upon the behavior of the oscillations. In

fact, this assumption has been supported by actual measurements (see, for instance, L. Collenbusch, Annalen der Phys., (5), vol. 13, 1932, p. 191).

It follows from this fact, and it has been confirmed by experiment that (1) for'the observed type of oscillation the behavior of the electrons in the grid-anode space alone is governing and decisive; and (2) in this scheme the grid is called upon to fulfill two contradictory or conflicting functions, to wit: (a) by virtue of its high positive potential it must cause the electrons to assume the requisite velocity and to pass into the grid-anode space; and (b) the grid must serve as a gathering or collector electrode for such electrons as are reversed in a plane anterior to the retarding electrode.

These two opposed functions of the grid are further discussed in the following:

If the grid is to permit great numbers of electrons to fly through at the desired rate of speed, it must be wide-meshed, and be made of slender wires so that the resultant, absorption cross-section for the electrons will be reduced. If, on the other hand, the grid is expected to gather such electrons as are flying back from the reversing surface or plane, it should have a large absorption cross-section. As a matter of fact, by varying this last named cross-section (number of grid wires and spacing between them) a type 5 of grid may be found which providesthe most favorable conditions for the generation of waves. However, in this connection it is inevitable that the grid will absorb the. major portion of the electrons before they have had a chance to tra- 5 verse the grid-anode space and to generate oscillations. It has been pointed out in several quarters that, as a matter of fact, this large absorpcuit schemes.

Retarding-field or electron-oscillation circuit organizations have been suggested in the earlier art in which the accelerator or grid electrode have apertures which correspond to the form of the cathode. In tubes of this'sort the provision of a magnetic field has two advantages. One is to produce a virtual cathodeclose to the accelerator electrode. The other advantage is to insure concentration or focusing of the electron stream.

Now, the present invention is concerned with tubes which are adapted to a solution of the same fundamental problem. However, for tubes as here disclosed a further advantage may be emphasized that concentration of the electron current is insured alone by choosing a suitable shape for the accelerator electrode. Thus it becomes entirely unnecessary to provide an additional magnetic fleld such as would require the use of ferro-magnetic electrode materials and of cer-. tain impractical shapes of electrodes.

My invention deals with a retarding-field or electron-oscillation tube in which the acceleration electrode between cathode and electron-oscillation or positive-grid tube is so formed that the number of electrons reaching the accelerator electrode directly from the cathode is minimized. The outstanding featured this tube is that the accelerator electrode has one or more convex surfaces facing the cathode, and that it is apertured in a region directly opposite the cathode.

In order that the generation of oscillations may be localized chiefly in the space between the the cathode becomes constricted or concentrated and results in a beam or band about the shortest line connecting the cathode and the accelerator electrode. If, then, the aperture in the apex of the accelerator electrode is not made unduly large so that the focusing action secured by the appropriate shape of the accelerator electrode is preserved, the focused electron stream will pass across the said aperture without an undue volume of such electrons being directly and immediately absorbed by the accelerator electrode. After the electrons have traveled through the space bechanged into oscillatory energy, they should naturally be gathered by the said accelerator electrode or grid,

To practice this basic idea of the invention manifold forms of electrode are conceivable. A number of preferred forms are illustrated, by way of example, in Figs. 1 to 5, without it being intended to thereby exhaust actual possibilities.

Fig. 1 shows a comparatively simple embodiment of the fundamental idea of the invention. The cathode K is made straight. The accelerator electrode G and the retarder electrode 13 are mounted so that their axes will be parallel to the cathode. They have the shape of cylindrical or parabolic segments. The accelerator electrode G which has a positive biasing voltage in relation to the cathode has an aperture in its apex matching roughly the form of the cathode. In order to insure an additional focusing effect upon the electron current, negatively biased director electrodes R may be disposed in the neighborhood of the cathode.

Fig. 2 shows a tube form resembling that in Fig. 1, with this distinction, however, that the accelerator electrode is divided by the aperture A into'two equal parts G and G". -The;oscillatory circuits to be excited being in the form of a Lecher-wire line L and L" is interposed between the said two halves of electrode G.

The tube shown in Fig. 3 is a complete pushpull arrangement. In symmetric relation to the cathode K are two accelerator electrodes GI and G2 presenting apertures AI and A2, respectively. Connected with the accelerator electrodes is the oscillatory circuit LC. Posteriorly of each of the accelerator electrodes is a convenient retarder electrode BI and B2, respectively. For additional focusing or concentrator action the cathode is surrounded by an annular director electrode R. This electrode R is placed in a plane at right angles to the line connecting the apertures Al and A2.

Fig. 4 shows a further development of the idea upon which this invention is predicated. The whole electrode assembly presents a structure of cylindrical symmetry. In the axis of the system is the retarding electrode B having the form of a cylinder. Concentric in reference theretoupon a circle of larger diameter is the accelerator electrode G comprising a plurality of cylindrical segments parallel to the axis and being regularly spaced apart around the periphery. In front of the apertures, i. e., the apertures A of the accelerator electrode G are placed the cathodes. The segments G are directly connected with one another at least for radio frequency currents so that their alternating potentials will always be in phase.

The electrode assembly as just described constitutes an extension of a concentric or co-axial conductor transmission line leading to a utiliza-- tion device, say, a radiator element St. The length of the electrode system including the attached resonant system may be, for instance, equal to M4 or a multiple thereof. At a place where there is a voltage node, the outer conductor is connected to a screen Sch and the inner conductor is connected to a radiator St. The screen Sch represents an artificial ground in reference to the radiator St. The radius of the screen may also be chosen preferably equal to M4. The electrode system and at least a part of the adjacent tubular line is enclosed in a gas-tight vessel V.

Fig. 5 shows a somewhat different system of electrodes. The cathode K is punctiform and the other electrodes have the shape of shallow hemispheric dishes. The resonant system in the form of a concentric conductor line merges into the electrode system in such a way that the cupshaped (hemispheric) electrodes, that is, accelerator and retarder electrodes, form at one end the termination-of the inner and the outer conductors. The concentric conductor system, at a distance of M4 from the electrode assembly may be connected, if desired, to a parallel-wire line or Lecher-wire system. Of course, all such factors must here be duly taken into consideration which are essential in changing a dissymmetric energy line into a symmetric line.

The retarding electrode, if desired, may be replaced by a sort of counter-cathode for the purpose of enhancing the energy yield or output. Inasmuch as the outer form of the retarding electrode must, as far as feasible, be preserved so as to preserve the field conditions, it will be advisable to indirectly heat the counter-cathode, whether the same is planar or solid.

The director electrodes R as shown in Fig. 3, may be usedadvantageously, although in some instances they are not absolutely essential.

The fundamental idea of the invention is to make or form the accelerator electrode so that it has a positive bias in respect of the cathode. By so doing the electrons when traveling away from the cathode will be markedly accelerated, while absorbing a minimum number of electrons. The invention is not restricted to oscillator tubes and circuits. In fact, it couldjust as well be adopted in arrangements serving for amplification, frequency multiplication and, if'necessary, reception of oscillations.

Moreover, the form of construction of the accelerator electrode or grid hereinbefore disclosed is not confined to retarding field or electron-oscillation tubes. In fact, it is within the sense and scope of this invention to include also tubes in which the electrons, after they have participated in the excitation of oscillations, are allowed to impinge upon the counterelectrode B and to produce secondary emission therefrom so as to boost the generation and wave excitation process and maintain the same.

I claim:

1. A braking field oscillator tube having at least three electrodes including emissive, accelerator and repulsion electrodes, the accelerator and repulsion electrodes being conformed to curved surfaces the convex sides of which are opposed to the direction of primary emission, and the accelerator electrode being apertured in zones nearest the sources of primary emission.

2. A braking field oscillator tube having a single linear cathode, a retarding field electrode having a convex surface which faces toward the cathode, and a pair of accelerator electrodes, the two electrodes of. said pair being conformed to a single curved surface the-convex sides of which face toward the cathode, and being separated from one another by a space in direct line between the cathode and the retarding field electrode.

'ments each disposed in juxtaposition to the spaces between adjacent ones of the accelerator electrodes.

4. An electron discharge tube according to claim 3 and having portions of said retardingfleld electrode and'of said accelerator electrodes extending exteriorly of said envelope.

5. Tube organization as claimed in claim 3 wherein the segments are connected directly with one another. v

6. A braking field oscillator tube having a cathode, an apertured'electrode the surfaces of which are respectively convex and concave, the convex surface facing said cathode, another electrode adapted to function as a retard electrode, the last said electrode having a convex surface which faces the concave side of said apertured electrode and is in the direct path of. electrons projected from the cathode through the opening of said apertured electrode;

7. An electron discharge tube in accordance with claim 6 and having said apertured electrode conformedto a cylindricalsurface.

8. An. electron discharge tube in accordance with claim 6 and having said apertured electrode conformed to a parabolic surface.

9. An electron discharge tube in accordance with claim 6 and having said apertured electrode cup-shaped. I

RICHARDSEILER. 

